Many delivery devices exist for the delivery of powdered substances, such as disclosed in the applicant's earlier WO-A-2000/051672.
Whilst these delivery devices have found extensive application, the present inventors have recognized the need for a delivery device which utilizes the exhalation breath of a user as the driving force to deliver a metered dose of powdered substance, and in particular which is of low cost, such as to allow for use in high-volume applications, typically in the delivery of vaccines.
The present inventors have also recognized the need for a compact device, which in one embodiment allows for manual actuation, thus allowing for operation in emergency situations, such as when the subject is unconscious.